1. Power on the system and while the “TOSHIBA” logo appears, press F2 key to enter the BIOS Setup Menu.
2. Select Security tab and set the Secure Boot to Disabled.

3. Select Advanced tab and go to System Configuration.
4. Set the Boot Mode to CSM Boot.

5. Press F10 key to save and exit.
6. Press F12 key at “TOSHIBA” logo screen to toggle between the bootable devices and choose the medium which you want to boot from.
If you were a complete nugget like me, you can lock up the BIOS all together, in which case you have to remove all power (AC / Battery) and hold the power button for 20 seconds to hard reset the BIOS. Then access via F2 key immediately
Note: Sometimes Hard resetting the BIOS removes the “Secure Boot” feature

This then allows Windows 7 CD Installer to Run if you want to downgrade by pressing F12 and choosing boot medium CD / USB